Connecting rod bearing shell or bushing or main bearing shell

ABSTRACT

The invention relates to a connecting rod bearing shell or bushing for internal combustion engines or to a main bearing shell for crankshaft mounting in internal combustion engines, made of a sliding bearing composite material having a metal, preferably steel support layer and a metal sliding layer applied thereto. The sliding bearing composite material is suitable for all applications cited and the sliding layer is made up of a copper zinc alloy with 10-25 wt. % Zn. 1-3 wt. % Mn. 1-3 wt. % Ni. 2-6 wt. % Fe: the remainder being copper, and impurity elements, respectively accounting for a maximum of 0.1%, corresponding to a maximum overall sum of 1 wt. % and the sliding layer is exclusively crystallised in the α-phase.

This application is the national stage of PCT/EP02/09380 filed on Aug.22, 2002 and also claims Paris Convention priority of DE 101 44 126.6filed on Sep. 8, 2001.

BACKGROUND OF THE INVENTION

The invention concerns a connecting rod bearing shell or bushing forinternal combustion engines or a main bearing shell for bearing thecrankshaft of internal combustion engines, made from a sliding bearingcomposite material with a metallic, preferably steel, support layer, andwith a metallic sliding layer disposed thereon.

Connecting rod bearing elements, i.e. connecting rod bearing shellssurrounding the crank pin of a crankshaft, and connecting rod bearingbushings which surround the piston bolt and can be pressed into thesmall end bearing, must meet multiple requirements. On the one hand, theconnecting rod bearing shells must be durable at high sliding speeds andaverage loads, and the connecting rod bearing bushings must be durableat high loads and higher temperatures but slower to moderate slidingspeeds. The requirements for main bearing shells in crankshafts aredetermined by the reduced load at these locations compared to connectingrod bearing shells and the high sliding speed at relatively moderatetemperatures. Main bearing shells must also be able to compensate formisalignment of the crankshaft.

The Assignee has disclosed connecting rod bearing bushings for use inthe small connecting rod eye of an engine connecting rod whose slidinglayer consists of a copper zinc alloy having a relatively large zincportion of approximately 30% by weight and 2% by weight of manganese, 2%by weight of nickel, 2% by weight of aluminium and 1.8% by weight ofiron.

EP 1 158 062 A1 discloses a copper zinc aluminium wroughting materialand its use for producing bearing bushings for connecting rods andpistons in internal combustion engines. The material consists of 63.5 to66.5% by weight of copper, 2.0 to 5.4% by weight of aluminium, 4.1 to4.9% by weight of manganese, 2.6 to 3.4% by weight of iron, 1.1 to 1.9%by weight of nickel, the rest being zinc and the usual impurities. Theembodiments disclose a zinc content of 20 or 22% by weight.

DE 44 11 762 A1 discloses a sliding layer composite material wherein acopper-zinc wroughting alloy having a large zinc portion of 28 to 32% byweight is roll-bonded to a support layer of steel.

DE 198 01 074 A1 discloses a sliding layer composite material with acopper zinc alloy having a proposed ratio between α and β phase of 1.5to 6.

CH 223 580 discloses copper zinc alloys, in particular for producingmachine parts which are exposed to frictional loads, with 2 to 8% byweight of aluminium, 0.05 to 3% by weight of silicon, 0.5 to 10% byweight of manganese and 50 to 70% by weight of copper. Up to 10% byweight of lead and 0.1 to 5.0% by weight of iron, nickel and cobalt maybe added to the alloy.

DE 197 28 777 C2 discloses a layered composite material having a carrierlayer and a metal bearing layer, in particular made from a copper zincalloy and with an electro-plated lead-free sliding layer on the basis oftin.

In view of the above, it is the underlying purpose of the presentinvention to produce a sliding layer composite material which issuitable for use as connecting rod bearing shell and also for use asconnecting rod bearing bushing and main bearing shell for thecrankshaft.

SUMMARY OF THE INVENTION

This object is achieved in accordance with the invention in that thesliding layer of the connecting rod bearing shell or connecting rodbearing bushing or main bearing shell is formed by a copper zinc alloywhich comprises 10-25% by weight of Zn, 1 to 3% by weight of Mn, 1 to 3%by weight of Ni and 2 to 6% by weight of Fe, the rest being copper andimpurities, each of which has a maximum of 0.1% by weight and a totalimpurity maximum of 1% by weight, wherein the sliding layer iscrystallized exclusively in the α phase.

It has turned out that when the copper zinc alloy crystallizesexclusively in the α phase, a sliding bearing material is obtained whichis suitable for the mentioned applications and which has excellentproperties with regard to corrosion. β brass tends to selectivelycorrode and behaves as a sacrificial anode in the metallic connectingrod. The high iron content has solidifying properties and increases thetoughness of the material. It reduces the grain size and increases there-crystallization temperature of the alloy. The iron content ispreferably 3.5 to 4.5% by weight.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention has shown that when the zinc content is limited to 25% byweight, a structure is achieved which is crystallized exclusively in theα phase.

Moreover, it is particularly advantageous when the sliding layerconsists of the above-mentioned components or of an alloy which containsan additional 1 to 3% by weight of aluminium. Aluminium increases thestrength of the inventive alloy.

It is also advantageous to form a thin overlay layer on the slidinglayer, which faces the sliding partner and has an electro-plated tinlayer or a tin layer with PTFE inclusions or a layer of an aluminium tinalloy sputtered onto a diffusion-blocking layer. When the overlay layeris to serve as running layer, the layer thickness is chosen to be morethan 10 μm and if it is to serve merely as run-in layer, the layerthickness is selected to be <5 μm.

A preferred composition of the sliding layer of the inventive connectingrod bearing shell or connecting rod bearing bushing has a composition in% by weight of Cu(rest) Zn(19-21), Mn(1.5-2.5), Ni(1.5-2.5),Fe(3.5-4.5), Al(1.5-2.5). Particularly preferred is a sliding layer ofCuZn20Mn2Ni2Fe4Al2 alloy.

1. A connecting rod bearing shell or bushing for a combustion engine ora main bearing shell for bearing the crankshaft of a combustion engine,made from a sliding bearing composite material comprising: a metallicsupport layer; and a metallic sliding layer disposed thereon, whereinsaid sliding layer has a copper zinc alloy with 10 to 25% by weight ofZn, 1 to 3% by weight of Mn, 1 to 3% by weight of Ni, 2 to 6% by weightof Fe, the rest being copper and impurities of not more than 0.1% byweight each, in total not more than 1% by weight, said sliding layerbeing crystallized exclusively in an α phase.
 2. The connecting rodbearing shell or bushing for a combustion engine or main bearing shellof claim 1, wherein said metallic support layer is made from steel. 3.The connecting rod bearing shell or bushing or main bearing shell ofclaim 1, wherein said sliding layer further comprises a thin overlaylayer, facing a sliding partner, said overlay layer being one of anelectro-plated layer of tin, an electroplated layer of an alloy on thebasis of tin, a tin layer with PTFE inclusions, and a layer of analuminium tin alloy sputtered onto a diffusion-blocking layer.
 4. Theconnecting rod bearing shell or bushing or main bearing shell of claim1, wherein said the sliding layer additionally comprises 1 to 3% byweight of Al.
 5. The connecting rod bearing shell or bushing or mainbearing shell of claim 1, wherein an iron content is 3.5 to 4.5% byweight thereof.